Devices have already been proposed for enabling motor vehicles to run on a flat tire, which devices are constituted by an elastomer ring mounted on the rim of a wheel inside the pneumatic tire fitted to the wheel, the elastomer ring having an annular base clamped onto the rim and holding the beads of the tire pressed against the margins of the rim, and a radially-projecting annular portion extending towards the tread of the tire and serving, in the event of a severe loss of pressure in the tire, as an abutment for pressing against the zone of the tread of the tire which is in contact with the ground, and preventing the walls and the tread of the tire being crushed or damaged by the margins of the rim, thereby enabling the driver of the vehicle to keep on driving without having to stop immediately to change the wheel.
Until now, attempts have been made to reduce the size of these "running rings" as much as possible, both with respect to the radial extent thereof inside a tire and with respect to the width or axial extent thereof so as to diminish their weight and their cost while retaining the possibility of running at least several tens of kilometers on a flat tire and at a speed of at least 50 km/h to 60 km/h under acceptable conditions of safety.
It has thus been possible, for private vehicles, to develop flat tire running devices that are lightweight (a few kilograms) and that provide very high performance since they make possible to travel more than 150 km at a speed of about 80 km/h while retaining good road handling when cornering and braking, to such an extent that the driver of the vehicle is not always aware of running on a flat tire.
Flat tire running devices of this type have also been developed for military vehicles, comprising running rings that are heavier and more robust than those for private vehicles, but that have nevertheless been lightened and reduced in size as much as possible in order to reduce cost and avoid degrading vehicle mobility.